title: A novel growth stimulating activity from BRL-3A cell conditioned medium.
abstract: The R- cell line is a 3T3-like cell line originating from mouse embryos with a homozygous disruption of the type 1 insulin-like growth factor receptor (IGF-IR) genes. Although R- cells cannot grow at all in serum-free medium (SFM) supplemented by several known growth factors, either singly or in combination, they are able to grow in 10% serum, albeit at a reduced rate. These findings suggested that serum contains an unknown, or unidentified, growth factor that can promote cell growth even in cells devoid of IGF-IRs. In an effort to identify such growth factor, we searched, using R- cells, for a growth and DNA synthesis stimulating activity in SFM conditioned by different cell lines. We found that the BRL-3A cell line secreted an activity capable of stimulating DNA synthesis and cell proliferation in R- cells. This activity (which is concentration-dependent) can be collected and concentrated by ultrafiltration, it is heat-labile, proteinase K-sensitive and has a size larger than 10 kDa. Because of the resistance of R1 cells to stimulation by known growth factors, we believe that this activity is due to a novel polypeptide secreted by BRL-3A cells. Further characterization of the active component(s) is in progress.
authors.affiliation: Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: S Q
authors.initials: SQ
authors.lastname: Xu
authors.forename: C
authors.initials: C
authors.lastname: Sell
authors.forename: G C
authors.initials: GC
authors.lastname: DuBois
authors.forename: R
authors.initials: R
authors.lastname: Baserga
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D004261:DNA Replication; D019286:Endopeptidase K / Q000378:metabolism; D005347:Fibroblasts; D006133:Growth Substances / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D006358:Hot Temperature; D051379:Mice; D008970:Molecular Weight; D017526:Receptor, IGF Type 1 / Q000502:physiology
chemical_list: D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D006133:Growth Substances; D017526:Receptor, IGF Type 1; D019286:Endopeptidase K